Comments and/or questions?
Web Master

Eastern Larch Beetle

by
Bruce Matson

      One of the more common insects causing mortality of tamarack/eastern larch in the Maritimes is the Eastern Larch Beetle (Dendroctonus simplex LeConte). These small dark brown beetles(3.5 to 5mm long) and their larvae tunnel through the inner bark (phloem and cambium) of the main bole of the trees. This effectively cuts off the circulation of sap through the tree and mortality occurs within a few years.

      Conifer bark beetles, of which the eastern larch beetle is a family member, typically attack trees that are already under stress from other insects or environmental factors. The larch beetle however appears to infest seemingly healthy stands. Most stands of tamarack that I see with significant mortality are semi-mature to mature and growing on abandoned pastures or fields. The soils are often imperfectly drained and white spruce is a common associate. These essentially human induced forest communities on old agricultural ground seem to lack ecosystem components that provide tamarack and white spruce with much greater longevity in their natural environments.

      So how can you identify an eastern larch beetle attack? The presence of one tree to many hectares of standing dead semi-mature tamarack is a good place to start. Shortly after the trees die the bark on the lower tree bole begins to slough off. The feeding galleries should be readily apparent both under the bark and on the surface of the wood of the standing tree. The problem for many woodlot owners is that once dead trees are identified in a stand, the beetles are already well established.

Bruce Matson, RPF
Extension Forester
NB Forest Extension Service, DNRE
Box 150, Hampton NB, E0G 1Z0
506-832-6171
bematson@gov.nb.ca
http://www.gov.nb.ca/dnre/fes/index.htm